Prev: [PATCH] drivers/serial/sunsab.c: adjust the constant used to initialize the interrupt_mask0 fields
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From: H Hartley Sweeten on 12 Mar 2010 12:20
It's usually more convenient to set the backlight brightness
as a 'percent' of total brightness rather than using the raw
'brightness' value.

This provides the necessary sysfs attributes to handle this.

Signed-off-by: H Hartley Sweeten <hsweeten(a)visionengravers.com>
Cc: Richard Purdie <rpurdie(a)rpsys.net>

---

diff --git a/drivers/video/backlight/backlight.c b/drivers/video/backlight/backlight.c
index 18829cf..af25bfa 100644
--- a/drivers/video/backlight/backlight.c
+++ b/drivers/video/backlight/backlight.c
@@ -190,6 +190,50 @@ static ssize_t backlight_show_actual_brightness(struct device *dev,
return rc;
}

+static ssize_t backlight_show_percent(struct device *dev,
+ struct device_attribute *attr, char *buf)
+{
+ struct backlight_device *bd = to_backlight_device(dev);
+ int percent;
+
+ percent = bd->props.brightness * 100 / bd->props.max_brightness;
+ return sprintf(buf, "%d\n", percent);
+}
+
+static ssize_t backlight_store_percent(struct device *dev,
+ struct device_attribute *attr, const char *buf, size_t count)
+{
+ struct backlight_device *bd = to_backlight_device(dev);
+ unsigned long percent, brightness;
+ int rc;
+
+ rc = strict_strtoul(buf, 0, &percent);
+ if (rc)
+ return rc;
+
+ brightness = percent * bd->props.max_brightness / 100;
+
+ rc = -ENXIO;
+
+ mutex_lock(&bd->ops_lock);
+ if (bd->ops) {
+ if (brightness > bd->props.max_brightness)
+ rc = -EINVAL;
+ else {
+ pr_debug("backlight: set to %lu%% (brightness of %lu)\n",
+ percent, brightness);
+ bd->props.brightness = brightness;
+ backlight_update_status(bd);
+ rc = count;
+ }
+ }
+ mutex_unlock(&bd->ops_lock);
+
+ backlight_generate_event(bd, BACKLIGHT_UPDATE_SYSFS);
+
+ return rc;
+}
+
static struct class *backlight_class;

static int backlight_suspend(struct device *dev, pm_message_t state)
@@ -233,6 +277,7 @@ static struct device_attribute bl_device_attributes[] = {
__ATTR(actual_brightness, 0444, backlight_show_actual_brightness,
NULL),
__ATTR(max_brightness, 0444, backlight_show_max_brightness, NULL),
+ __ATTR(percent, 0644, backlight_show_percent, backlight_store_percent),
__ATTR_NULL,
};

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Prev: [PATCH] drivers/serial/sunsab.c: adjust the constant used to initialize the interrupt_mask0 fields
Next: regulator: Get rid of lockdep warning